Solid-state image sensor, distance measurement apparatus including the solid-state image sensor, and camera

ABSTRACT

A solid-state image sensor including a plurality of pixels each including a photoelectric conversion element formed on a semiconductor. The solid-state image sensor includes a distance measurement pixel including a plurality of photoelectric conversion elements configured to acquire signals for distance measurement and included in at least a part of the plurality of pixels, and a control electrode disposed on the semiconductor via an insulating film, wherein the control electrode is configured to control positions or shapes of the photoelectric conversion elements by applied voltages, while the distance measurement pixel maintains the number of the plurality of photoelectric conversion elements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One disclosed aspect of the embodiments relates to a solid-state imagesensor, a distance measurement apparatus including the solid-state imagesensor, and a camera, and, more particularly, to the solid-state imagesensor for distance measurement, which is used for distance measurementof a digital still camera or a digital video camera.

2. Description of the Related Art

In a digital still camera or a video camera, a solid-state image sensor,in which distance measurement pixels having a distance measurement(focus detection) function are arranged in all or a part of pixels ofthe solid-state image sensor to measure a distance in a phase differencemethod, is discussed in Japanese Patent No. 4027113. The distancemeasurement pixel includes a plurality of photoelectric conversionelements, and is configured such that light flux passing throughdifferent exit pupil areas of a imaging lens is guided to differentphotoelectric conversion elements. By using the plurality of distancemeasurement pixels, the distance measurement function detects images bylight flux passing through different exit pupil areas (an image A and animage B, respectively) to measure a deviation amount of the image A andthe image B. The distance measurement function calculates a defocusamount from the deviation amount and a base length (an interval betweendifferent exit pupil areas) to measure a distance (to detect a focusposition).

In this case, an exit pupil surface of the imaging lens and a surface ofthe photoelectric conversion element have a substantially opticalconjugate relation. Therefore, an exit pupil area, through which lightflux passes, is determined according to the position or size of thesurface of the photoelectric conversion element. For example, when acenter of gravity of the photoelectric conversion element is arrangedoutward from a central axis of the distance measurement pixel, the exitpupil, through which light flux passes, is shifted to the outside of thepupil. Hence, the base length is lengthened. Also, when thephotoelectric conversion element is enlarged, the exit pupil area,through which light flux passes, is enlarged. Therefore, light quantityreceived by the photoelectric conversion element is increased andsensitivity is increased accordingly.

However, in the actual distance measurement and image capture, theoptimal base length or sensitivity (the position and size of thephotoelectric conversion element) varies according to luminance of anobject or a imaging condition (a defocus amount). For example, when thedistance is measured with high accuracy, the base length needs to belengthened. Also, in the case of a low-luminance object, noise increasesand distance accuracy worsens. Therefore, the sensitivity needs to beincreased by enlarging the area of the photoelectric conversion element.However, in the conventional methods, when distance measurement pixelsare designed, the base length is uniquely determined. Therefore, anoptimal distance measurement could not be achieved according to theobject or the photographing condition.

SUMMARY OF THE INVENTION

One disclosed aspect of the embodiments is directed to a solid-stateimage sensor capable of performing distance measurement with highaccuracy according to an object or a imaging condition, a distancemeasurement apparatus including the solid-state image sensor, and acamera.

According to an aspect of the embodiments, a solid-state image sensorincluding a plurality of pixels each including a photoelectricconversion element formed on a semiconductor includes a distancemeasurement pixel including a plurality of photoelectric conversionelements configured to acquire signals for distance measurement andincluded in at least apart of the plurality of pixels, and a controlelectrode disposed on the semiconductor via an insulating film, whereinthe control electrode is configured to control positions or shapes ofthe photoelectric conversion elements by applied voltages, while thedistance measurement pixel maintains the number of the plurality ofphotoelectric conversion elements.

According to exemplary embodiments, it is possible to realize asolid-state image sensor capable of performing distance measurement withhigh accuracy according to an object or a imaging condition, a distancemeasurement apparatus including the solid-state image sensor, and acamera.

Further features and aspects of the disclosure will become apparent fromthe following detailed description of exemplary embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the disclosure and, together with the description, serveto explain the principles of the disclosure.

FIG. 1 is a diagram illustrating a distance measurement apparatus usinga solid-state image sensor according to a first exemplary embodiment.

FIG. 2 is a schematic cross-sectional view illustrating a distancemeasurement pixel in the solid-state image sensor according to the firstexemplary embodiment.

FIG. 3 is a diagram illustrating a method for measuring a distance to anobject by using the solid-state image sensor according to the firstexemplary embodiment of the present invention.

FIG. 4A is a diagram illustrating a method for controlling thesolid-state image sensor according to the first exemplary embodiment.FIG. 4B is a diagram illustrating the electron energy of the elementsaccording to the first exemplary embodiment.

FIG. 5A is a diagram illustrating a method for controlling thesolid-state image sensor for an image A according to the first exemplaryembodiment. FIG. 5B is a diagram illustrating the electron energy of theelements for the image A according to the first exemplary embodiment.FIG. 5C is a diagram illustrating a method for controlling thesolid-state image sensor for an image B according to the first exemplaryembodiment. FIG. 5D is a diagram illustrating the electron energy of theelements for the image B according to the first exemplary embodiment.

FIG. 6A is a diagram illustrating a method for controlling thesolid-state image sensor for high speed capture of an image A accordingto the first exemplary embodiment. FIG. 6B is a diagram illustrating theelectron energy of the elements for high speed image capture of an imageA according to the first exemplary embodiment. FIG. 6C is a diagramillustrating a method for controlling the solid-state image sensor forhigh speed capture of an image B according to the first exemplaryembodiment. FIG. 6D is a diagram illustrating the electron energy of theelements for high speed image capture of an image B according to thefirst exemplary embodiment

FIG. 7A is a diagram illustrating an initial phase of a process formanufacturing the solid-state image sensor including the distancemeasurement pixel according to the first exemplary embodiment. FIG. 7Bis a diagram illustrating a process to form electrodes for a process formanufacturing the solid-state image sensor including the distancemeasurement pixel according to the first exemplary embodiment. FIG. 7Cis a diagram illustrating a process to form interconnections, contactholes, and interconnection for a process for manufacturing thesolid-state image sensor including the distance measurement pixelaccording to the first exemplary embodiment. FIG. 7D is a diagramillustrating a process to form planarizing filter, color filter, andmicrolense for a process for manufacturing the solid-state image sensorincluding the distance measurement pixel according to the firstexemplary embodiment.

FIG. 8 is a schematic cross-sectional view illustrating a distancemeasurement pixel in a solid-state image sensor according to a secondexemplary embodiment.

FIG. 9 is a diagram illustrating an incident angle sensitivitycharacteristic of the solid-state image sensor according to the secondexemplary embodiment.

FIG. 10A is a diagrams illustrating a method for controlling thesolid-state image sensor according to the second exemplary embodiment.FIG. 10B is a diagram illustrating an electron energy of the imageelements of FIG. 10A according to the second exemplary embodiment.

FIG. 11A is a diagram illustrating a method for controlling thesolid-state image sensor according to the second exemplary embodiment.FIG. 11B is a diagram illustrating an electron energy of the imageelements in FIG. 11A according to the second exemplary embodiment.

FIG. 12 is a schematic top view illustrating a distance measurementpixel in a solid-state image sensor according to an exemplary embodimentother than the first and second exemplary embodiments.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the disclosurewill be described in detail below with reference to the drawings.

Hereinafter, a distance measurement apparatus including a solid-stateimage sensor according to each exemplary embodiment of the disclosurewill be described. In the exemplary embodiment, as an example of animage pickup apparatus including the distance measurement apparatus, adigital still camera will be described, but the present exemplaryembodiments are not limited thereto. Also, in the following descriptionwith reference to the drawings, the same reference numerals are assignedto components having the same function throughout all the drawings, andredundant description thereof will not be repeated.

Hereinafter, a first exemplary embodiment will be described. A distancemeasurement apparatus including a solid-state image sensor, to which theconfiguration of the present exemplary embodiment is applied, will bedescribed. Referring to FIG. 1, a distance measurement apparatus 100includes a imaging lens 101, a solid-state image sensor 102, and acalculation unit 103. In order to acquire distance information of anobject, an image is formed on the solid-state image sensor 102 by theimaging lens 101, and an image A and image B of the object are acquiredby a distance measurement pixel group disposed in the solid-state imagesensor 102. Information of the acquired image A and image B istransmitted to the calculation unit 103, which calculates distanceinformation of the object from a relation between a deviation amount anda base length.

A configuration of a solid-state image sensor including a pixel, whichmeasures a distance by a photoelectric conversion element in asemiconductor, according to the exemplary embodiment will be describedwith reference to FIG. 2. In FIG. 2, a pixel 200 is a pixel included ina distance measurement pixel group arranged in a part of pixels of thesolid-state image sensor. The pixel 200 includes a P-type well 202 and asurface P+ layer 203 formed of a P-type, a first photoelectricconversion element 204, a second photoelectric conversion element 205,and floating diffusion portions (hereinafter, FD portions) 206 and 207formed of an N-type in a semiconductor 201. Also, control electrodes aredisposed on the semiconductor 201 through an insulating film.Specifically, a gate insulating film 208, gate electrodes 209 and 210,and control electrodes 211, 212 and 213 are disposed on the surface P+layer 203 side of the semiconductor 201.

Light incident on the pixel 200 is guided to the first photoelectricconversion element 204 and the second photoelectric conversion element205 through a light condensing unit 214, a color filter 215, and aplanarization layer 216. Light incident on the photoelectric conversionelements 204 and 205 are converted into electrons to be accumulatedwithin the photoelectric conversion elements 204 and 205. Subsequently,the distance measurement apparatus 100 transfers the electrons to the FDportions 206 and 207 by applying signals to the gate electrodes 209 and210, to detect each charge amount as an electrical signal.

The acquisition of distance information is performed as follows. Thesurface of the semiconductor 201 and the surface of an exit pupil 104 ofthe imaging lens 101 have a substantially optical conjugate relation.Therefore, the first photoelectric conversion element 204 and the secondphotoelectric conversion element 205 of the distance measurement pixelreceive light flux passing through different exit pupil areas (a firstarea 105 and a second area 106) (FIG. 3). In this case, the distance tothe object may be measured by a known method by using a deviation amountof the image A generated via a plurality of first photoelectricconversion elements 204 and the image B generated via a plurality ofsecond photoelectric conversion elements 205, and a base length 107.

Also, the acquisition of image capture information is performed asfollows. In order to acquire a captured image by using the distancemeasurement pixel, the signals from the entire photoelectric conversionelements (the first photoelectric conversion elements 204 and the secondphotoelectric conversion elements 205) disposed within the pixels areadded to obtain a captured signal passing through the entire exit pupilareas. Therefore, as in the general solid-state image sensor, an objectimage may be acquired in the entire pixels by using the distancemeasurement pixel.

Next, the operation principle of the present exemplary embodiment willbe described. In the exemplary embodiment, the distance measurementapparatus 100 applies voltages to the control electrodes 211, 212 and213 to enable dynamic control of the positions or shapes of the firstphotoelectric conversion element 204 and the second photoelectricconversion element 205. By applying a positive voltage to the controlelectrodes 211, 212 and 213, electron energy of the semiconductor 201around the control electrodes 211, 212 and 213 via the gate insulatingfilm 208 decreases. Therefore, an electron density increases and thesemiconductor 201 changes to an N-type semiconductor.

On the other hand, by applying a negative voltage to the controlelectrodes 211, 212 and 213, electron energy of the semiconductor 201around the control electrodes 211, 212 and 213 increases, so that anelectron density decreases. Therefore, the semiconductor 201 changes toa P-type semiconductor. The photoelectric conversion elements 204 and205 have a function of converting light into electrons and accumulatingthe generated electrons with lower electron energy than the surrounding.For this reason, the electron energy states of the photoelectricconversion elements 204 and 205 or the surroundings thereof arerelatively changed. Therefore, the positions or shapes of thephotoelectric conversion elements 204 and 205 may be controlled.

Also, by using the plurality of control electrodes 211, 212 and 213, theelectron energy distributions of the photoelectric conversion elements204 and 205 may be controlled with higher degree of freedom. Next, themeasurement accuracy of the distance measurement apparatus 100 will bedescribed when the control electrode 211 is disposed over the firstphotoelectric conversion element 204, the control electrode 212 isdisposed above the first photoelectric conversion element 204 and thesecond photoelectric conversion element 205, and the control electrode213 is disposed over the second photoelectric conversion element 205.When the control electrodes 211, 212 and 213 are disposed over thephotoelectric conversion elements 204 and 205, the electron energy fromthe photoelectric conversion elements 204 and 205 disposed immediatelybeneath the control electrodes 211, 212 and 213 may be efficientlycontrolled. Also, when the control electrodes 211, 212 and 213 aredisposed between the photoelectric conversion elements 204 and 205, theelectron energy around the photoelectric conversion elements 204 and 205may be efficiently controlled.

As a normal mode, when no voltages are applied to the control electrodes211, 212 and 213 (FIG. 4A), the electron energy distribution of thesemiconductor 201 is determined by a manufactured doping concentration.Since the photoelectric conversion elements 204 and 205 accumulateelectrons, the semiconductor 201 is formed of an N-type such that theelectron energy is lowered (FIG. 4B). In this case, since no voltagesare applied, power consumption is low. Therefore, long-time distancemeasurement or image capture measurement is enabled. Furthermore, whenthe first photoelectric conversion element 204 and the secondphotoelectric element 205 are formed to be bilaterally symmetric to acentral axis of the pixel, signals of the image A and the image B havinghigh signal-to-noise (SN) ratios may be obtained.

Furthermore, as a high-accuracy mode, when the distance measurement isperformed, the base length 107 needs to be lengthened. In this case, inthe distance measurement pixel for acquiring the image A (FIG. 5A), anegative potential is applied to the control electrode 211, a positivepotential is applied to the control electrode 212, and a zero potentialis applied to the control electrode 213. In this manner, the electronenergy distribution is obtained as illustrated in FIG. 5B. Inparticular, a center of gravity of the first photoelectric conversionelement 204 is displaced outward from the central axis of the pixel.Also, in the pixel for acquiring the image B which is disposed near thepixel for acquiring the image A (FIG. 5C), a zero potential is appliedto the control electrode 211, a positive potential is applied to thecontrol electrode 212, and a negative potential is applied to thecontrol electrode 213. In this manner, the center of gravity of thesecond photoelectric conversion element 205 is separated outward fromthe central axis of the pixel (FIG. 5D).

By using the image A and the image B mentioned above, the firstphotoelectric conversion element 204 and the second photoelectricconversion element 205 displaced outward from the central axis of thepixel may be obtained. Therefore, the base length 107 lengthens and thedistance measurement accuracy improves accordingly. Also, even when thecaptured image is acquired, the signal resulting from the addition ofthe signals from the photoelectric conversion elements 204 and 205within the pixel is sufficiently large. Therefore, a captured imagehaving a high SN ratio may be obtained.

In the case of a low-luminance object in a high-sensitivity mode, anoise is large and a distance measurement error is increased. In thiscase, in the pixel for acquiring the image A, a zero potential isapplied to the control electrode 211, a positive potential is applied tothe control electrode 212, and a negative potential is applied to thecontrol electrode 213. On the other hand, in the pixel for acquiring theimage B, a negative potential is applied to the control electrode 211, apositive potential is applied to the control electrode 212, and a zeropotential is applied to the control electrode 213. Therefore, the pixelhaving acquired the image A in the high-accuracy mode (FIGS. 5A, 5B, 5Cand 5D) is switched to acquire the image B, and the pixel havingacquired the image B is switched to acquire the image A. As a result,the high-sensitivity mode may be realized.

In this case, since the areas of the photoelectric conversion elements204 and 205 for the acquisition of the image A and the image Bincreases, the SN ratio required for the distance measurement may besecured. As described above, an area of the specific photoelectricconversion element 204 and 205 is increased by changing an area ratio ofthe photoelectric conversion elements 204 and 205 in the distancemeasurement pixel. In this manner, the SN ratio increases in such amanner that the distance is measured by using the signal from thephotoelectric conversion element having a large area. As a result, evenin the case of the low-luminance object, the measurement may beperformed with a small distance measurement error. In the exemplaryembodiment, the control electrodes 211, 212 and 213 may control thepositions or shapes of the photoelectric conversion elements 204 and 205by the applied voltages, while allowing the distance measurement pixelto maintain the number of the plurality of photoelectric conversionelements.

When it is unnecessary to acquire the distance information, a zeropotential is applied to the control electrode 211, a positive potentialis applied to the control electrode 212, and a zero potential is appliedto the control electrode 213. In this case, signals from the firstphotoelectric conversion element 204 and the second photoelectricconversion element 205 are added. In this manner, the signals from thephotoelectric conversion elements 204 and 205 may be acquired notseparately but simultaneously. Therefore, the read or processing timemay be shortened. As a result, high-speed image capture may be performed(FIGS. 6A, 6B, 6C, and 6D).

As described above, the distance measurement apparatus arranges thecontrol electrodes near the photoelectric conversion elements andapplies the voltages thereto, so that the apparatus may change theelectron energy distributions of the photoelectric conversion elementsand the surrounding thereof. Therefore, the apparatus may dynamicallycontrol the positions or shapes of the photoelectric conversionelements. In the exemplary embodiment, the control electrodes maycontrol the positions or shapes of the photoelectric conversion elementsby the applied voltages, while allowing the distance measurement pixelto maintain the number of the plurality of photoelectric conversionelements. In this manner, the image pickup apparatus may achieve thedistance measurement and the acquisition of the object image in anoptimal measurement mode according to the object or the imagingcondition.

Also, due to the dynamic change, the entire distance measurement pixelsmay be used for the distance information or the image captureinformation. Therefore, the distance measurement accuracy improves andthe SN ratio of the captured image improves. Also, in the exemplaryembodiment, aback side illumination type solid-state image sensor isused. In this case, since the control electrodes 211, 212 and 213 aredisposed on a side opposite a direction of light incidence, lightscattering and absorption by the control electrodes 211, 212 and 213disappear. Therefore, the use of the back side illumination typesolid-state image sensor may increase the sensitivity of the solid-stateimage sensor.

Next, a process for manufacturing the solid-state image sensor includingthe pixel 200 according to the exemplary embodiment will be describedwith reference to FIGS. 7A, 7B, 7C and 7D. First, the gate insulatingfilm 208 is formed on a surface of the silicon semiconductor 201 bythermal oxidation. In order to form the photoelectric conversionelements 204 and 205 and the FD portions 206 and 207 in thesemiconductor 201, a resist mask is formed at a predetermined positionby photoresist, and impurity ion implantation is performed.Subsequently, the resist mask is removed by ashing. A diffusion layer(not illustrated) is formed by the similar ion implantation method (FIG.7A). Furthermore, a polysilicon film is formed to form the gateelectrodes 209 and 210 configured to transfer electrons generated in thephotoelectric conversion elements 204 and 205, and the controlelectrodes 211, 212 and 213 configured to change the positions or shapesof the photoelectric conversion elements 204 and 205. Subsequently, thegate electrodes 209 and 210 and the control electrodes 211, 212 and 213are formed by etching the polysilicon in predetermined patterns by usinga photolithography process (FIG. 7B).

Subsequently, an interlayer insulating film 217, for example, a boronphosphorus silicon glass (BPSG) film, is formed on the semiconductor201, the gate electrodes 209 and 210, and the control electrodes 211,212 and 213, and planarization is performed with a chemical mechanicalpolishing (CMP) method. Subsequently, for electrical connection, aconnection hole, such as a contact hole 218, is formed on the interlayerinsulating film 217 to be electrically connected to other metalinterconnection. In a similar manner, an interconnection 219 is formedand covered with the interlayer insulating film 217 (FIG. 7C).Subsequently, the side of the semiconductor 201 opposite the gateinsulating film 208 is polished and thinned until the photoelectricconversion elements 204 and 205 are exposed. Subsequently, if needed, aplanarization film 216, a color filter 215, and a microlens 214 areformed (FIG. 7D).

Hereinafter, as a second exemplary embodiment, a distance measurementapparatus including a solid-state image sensor different from the firstexemplary embodiment will be described. Also, a description of the samecomponents as the first exemplary embodiment will not be repeated.

FIG. 8 is a cross-sectional view illustrating a distance measurementpixel of the solid-state image sensor according to the present exemplaryembodiment. Referring to FIG. 8, the solid-state image sensor includes adistance measurement pixel 300. In the exemplary embodiment, thedistance measurement pixel 300 includes two control electrodes 301 and302 which are respectively disposed on the central axis side of thedistance measurement pixel 300 above a first photoelectric conversionelement 204 and a second photoelectric conversion element 205. Also,incident light is incident from the same direction as gate electrodesand the control electrodes 301 and 302, and reaches the photoelectricconversion elements 204 and 205.

In this case, a waveguide structure 303 having a higher refractive indexthan the surrounding is included immediately above the photoelectricconversion elements 204 and 205 so that light may not be scattered orabsorbed in the gate electrodes and the control electrodes 301 and 302.Therefore, even when electrodes, such as the gate electrodes and thecontrol electrodes 301 and 302, are disposed, the incident light may beefficiently guided to the photoelectric conversion elements 204 and 205.Also, in this case, the first photoelectric conversion element 204 andthe second photoelectric conversion element 205 in the distancemeasurement pixel 300 have an asymmetric incident angle sensitivitycharacteristic to the incident angle of the incident light, asillustrated in FIG. 9.

The acquisition of distance information is performed as follows. Whenhaving the asymmetric incident angle sensitivity characteristicillustrated in FIG. 9, the first photoelectric conversion element 204receives light passing through the first area 105 in the exit pupil 104of the photoelectric lens 101. Also, the second photoelectric conversionelement 205 receives light passing through the second area 106 in theexit pupil 104 of the photoelectric lens 101. Therefore, even though aguide unit, such as the waveguide structure 303, is used instead of alight condensing unit, such as a lens, if the solid-state image sensorhas the asymmetric incident angle sensitivity characteristic, thesolid-state image sensor may similarly detect light flux from differentportions of the exit pupil 104. In this manner, the distance measurementapparatus may acquire the image A and the image B by using a pluralityof distance measurement pixels, and measure the distance from thedeviation amount and the base length with the similar method as thefirst exemplary embodiment.

Next, the operation principle of the present exemplary embodiment willbe described. When configured as illustrated in FIG. 8, by applyingvoltages to the control electrodes 301 and 302, the distance measurementapparatus may control the electron energy distribution around thephotoelectric conversion elements 204 and 205, and dynamically changethe positions or shapes of the first photoelectric conversion element204 and the second photoelectric conversion element 205. The change ofthe photoelectric conversion elements 204 and 205 and the distancemeasurement accuracy of the distance measurement apparatus in a statewhere the two control electrodes 301 and 302 are included will bedescribed.

As a normal mode, as illustrated in FIGS. 10A and 10B, when no voltagesare applied to the control electrodes 301 and 302 (FIG. 10A), theelectron energy distribution of the semiconductor 201 is determined by amanufactured doping concentration. Since the photoelectric conversionelements 204 and 205 accumulate electrons, the semiconductor 201 isformed of an N-type such that the electron energy is lowered (FIG. 10B).In this case, since no voltages are applied, power consumption is low.Therefore, long-time distance measurement or image capture is enabled.Furthermore, when the first photoelectric conversion element 204 and thesecond photoelectric conversion element 205 are formed to be bilaterallysymmetric from the center of the pixel, the SN ratio may increase inboth the image A and the image B.

Also, as a high-accuracy mode, when the distance measurement isperformed with high accuracy, a base length 107 needs to be lengthened.In this case, in the distance measurement pixel for acquiring the imageA and the image B (FIG. 11A), a negative potential is applied to thecontrol electrodes 301 and 302. In this manner, the electron energydistribution is obtained as illustrated in FIG. 11B. The centers ofgravity of the first photoelectric conversion element 204 and the secondphotoelectric conversion element 205 move outward away from the centralaxis of the pixel. By using the image A and the image B, the firstphotoelectric conversion element 204 and the second photoelectricconversion element 205 displaced outward from the central axis of thepixel may be obtained. Therefore, the base length 107 may be lengthened,and the distance accuracy improves accordingly.

As described above, by arranging the control electrodes 301 and 302 nearthe photoelectric conversion elements 204 and 205 and applying thevoltages thereto, the electron energy distributions of the photoelectricconversion elements 204 and 205 and the surrounding thereof changes.Therefore, the positions or shapes of the photoelectric conversionelements 204 and 205 may be dynamically controlled. In this manner, thedistance measurement apparatus may achieve the optimal distancemeasurement and the acquisition of object images according to the objector the imaging condition. Also, due to the dynamic change, the entiredistance measurement pixels may be used for the distance information orimage capture information. Therefore, the distance accuracy improves,and the SN ratio of the captured image improves.

In the first and second embodiments, the case where two photoelectricconversion elements are included within the distance measurement pixelhas been described. In this case, the photoelectric conversion elementhas only to be divided into two parts within the pixel. Therefore, thedistance measurement pixel may be configured without excessivelylowering the aperture ratio (the ratio of the entire photoelectricconversion element occupied in the pixel) and the capacity of thephotoelectric conversion elements. However, the number of thephotoelectric conversion elements within the distance measurement pixelis not limited to two. For example, as illustrated in FIG. 12, fourphotoelectric conversion elements may be included.

In this case, since the exit pupil may be divided vertically andhorizontally, the distance may be measured with high accuracy to anyobject on a vertical line or a horizontal line. In FIG. 12 illustratinga top view of the distance measurement pixel, the pixel includes fourphotoelectric conversion elements 401, four gate electrodes 402, andfour FD portions 403 to detect signals of incident light by therespective photoelectric conversion elements 401. In this case, byarranging a plurality of control electrodes 404, the distancemeasurement apparatus may achieve the optimal distance measurement andthe acquisition of object images according to the object or thephotographing condition as in the first and second embodiments.

While the disclosure has been described with reference to exemplaryembodiments, it is to be understood that the disclosure is not limitedto the disclosed exemplary embodiments. The scope of the followingclaims is to be accorded the broadest interpretation so as to encompassall modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No.2012-013007 filed Jan. 25, 2012, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A solid-state image sensor including a pluralityof pixels each including a photoelectric conversion element formed on asemiconductor, the solid-state image sensor comprising: a distancemeasurement pixel including a plurality of photoelectric conversionelements configured to acquire signals for distance measurement andincluded in at least apart of the plurality of pixels; and a controlelectrode disposed on the semiconductor via an insulating film, whereinthe control electrode is configured to control positions or shapes ofthe photoelectric conversion elements by applied voltages, while thedistance measurement pixel maintains number of the plurality ofphotoelectric conversion elements.
 2. The solid-state image sensoraccording to claim 1, wherein the control electrode is configured tochange electron energy distributions of the plurality of photoelectricconversion elements and therearound by the applied voltages.
 3. Thesolid-state image sensor according to claim 1, wherein the controlelectrode includes a plurality of control electrodes disposed in thedistance measurement pixel.
 4. The solid-state image sensor according toclaim 1, wherein the control electrode is disposed on each of theplurality of photoelectric conversion elements.
 5. The solid-state imagesensor according to claim 1, wherein the control electrode is disposedbetween the plurality of photoelectric conversion elements.
 6. Thesolid-state image sensor according to claim 1, wherein the plurality ofphotoelectric conversion elements has an asymmetric incident anglesensitivity characteristic.
 7. The solid-state image sensor according toclaim 1, wherein the plurality of photoelectric conversion elementsincludes a back side illumination type in which light incident on eachof the photoelectric conversion elements is incident from a directionopposite the control electrode.
 8. A distance measurement apparatuscomprising: a solid-state image sensor including a distance measurementpixel disposed in at least a part of a plurality of pixels, wherein thedistance measurement apparatus is configured to detect images by lightflux passing through different exit pupil areas of a imaging lens byusing the plurality of pixels to measure a distance based on a deviationamount of each of the images, and wherein the solid-state image sensorincludes the solid-state image sensor according to claim
 1. 9. Thedistance measurement apparatus according to claim 8, wherein thedistance measurement apparatus is configured to be switchable betweenmeasurement modes having different incident angle sensitivitycharacteristics according to the applied voltages.
 10. The distancemeasurement apparatus according to claim 8, wherein the controlelectrode is disposed near a central axis side of the distancemeasurement pixel in the plurality of photoelectric conversion elements,and wherein a base length is lengthened by displacing a center ofgravity of each of the plurality of photoelectric conversion elementsoutward from the central axis by the applied voltages.
 11. The distancemeasurement apparatus according to claim 8, wherein the controlelectrode is disposed near a central axis side of the distancemeasurement pixel in the photoelectric conversion elements, and whereinan area ratio of the plurality of photoelectric conversion elements inthe distance measurement pixel is changed by the applied voltages.
 12. Acamera comprising the distance measurement apparatus according to claim8.